Electric hammer



J. E BRYAN -Oct 13, 1931.

ELECTRIC HAMMER Filed March 12, 1928 2 W mum III II A 770/? NE) Patented Oct. 13, 1931 PATENT OFFICE JAMES E. BRYAN, OF SEATTLE, WASHINGTON ELECTRIC HAMMER Application filed March 12, 1928; Serial No. 261,104.

My invention relates to improvements in centrifugal rotary hammers and the general object of my invention is to simplify and increase the efiiciency of hammers of this nature.

A more specific object is to provide a centrifugal rotary hammer employing a relatively heavy hammer element which is kept near to the axis about which it is rotated thereby utilizing to the greatest possible extent the limited amount of power available foroperating said hammer.

A further object is to provide eflicient spring shock absorbing means for arresting the swinging movement of the hammer at the limit of its movement in both directions.

Other and more specific objects and ad vantages relative to vibration elimination and rapid withdrawal of the hammer from the point of striking contact after successive impacts, will be apparent from the following description taken in connection with the accompanyin g drawings.

In the drawings, Figure 1 is a view partly in elevation of a centrifugal rotary hammer constructed in accordance with my invention.

Fig. 2 is a detached view partly in elevation of the hammer element and mounting for the same showing the hammer in a retracted position.

Fig. 3 is a detached top edge view of the hammer assembly.

7 Referring to the drawings, throughout which like reference numerals designate like parts, 5 is a cylindrical hammer housing having at one side a substantially tangential guide bar 6 provided with a bushing 7 within which the cylindrical end 8 of a tool 9 is slidably disposed, the said cylindrical end 8 projecting into the housing 5 as shown in Fig. 1.

A centrifugal hammer and mounting for the same are disposed Within the housing 5. The hammer mounting comprises a block 10 recessed onone side as at'll for the reception of a hammer element 12 and having two bearing pins or studs 13 and 14 that project in opposite directions therefrom and are journaled in the housing 5. A portion 15 of solid metal extendsacross back of the recess 11 serving the double purpose of a counterweight and a means of uniting the two sides of said mounting as hereinafter explained. The hammer element is fulcrumed on apivot pin 16 whose center'is offset a short distance relative to the common center or axis of the studs 13 and 14, and in a manner such that, at the revoluble point of contact of the hammer to the tool 9, the plane of the hammer striking face will be in approximate right or acute angular relationship to a plane taken through both the axis ofthe base and hammer, the said pivot 16 constituting, in effect, a crank pin on which the hammer element mounted. An anvil piece 17 of suitable steei is inserted in the hammer element 12 for striking the blows on the end 8 of the tool."

' For absorbing the shock of the hammer as it rebounds from the tool, I provide a spring element 18 which maybe located in the bottom of the recess 11, and I also provide another spring element 19' with wvhich a shouldered projection 20of the hammer may engage for absorbing the shock of the hammer as it swings outwardly after passing the striking position. The movement of the spring element 19 is limited by the back wall of the recess 11 so that the hammer element will be positively stopped and can not swin further than the positionshown in Fig. 1, under the influence of centrifugal force.

The hammer assembly is driven by a gearwheel 22 which is rigidly secured to the hearing stud 13 and meshes with a pinion 23 on a shaft 24 that maybedirectly connected with an electric 'motorin a housing 25 that is rigidly secured to the housing 5. One or more handles 26 may be provided on the housings 25 and 5.

In the operationof this hammer, when the trifugal'force into the position shown in Fig. 1, the portion 20 coming in contact with the spring 19 which serves as a cushion, first to absorb the shock and then to positively limit the swinging movement of the hammer element-as the spring is forced againstthe back wall of the recess 11. When hammer element reaches the positionshown in Fig. 1 it will strike a blow on the end 8 of the tool, then, as the pivot 16 moves on around its crank circle, the hammer element will be withdrawn fromicontact, partly by rebound and partly by theeffective arcuate travel of crank pivot 16, being positioned as described in such relationship, at point of contact, with respect to the base rotation, asto afford the:

maximum movement per degree of travel in a rapid clearing of the anvil piece 17 vfrom tool 8, prior to the subsequent and-necessarily rapid centrifugal forcereaction of the hammer. More particularly, as the hammer element passes theend of the tool centrifugalv force is rapidly reasserted'to returnthe ham- 7 mer element into successive StIlklIlgTBlfltlOnship'with respect tothe tool, a blow upon each complete revolution of thehammer assembly. The'spring 18 absorbs'all shock of the rebound andihelps to throwthe, hammer element out quickly after it -.jhas passed the tool. The hammer, being mounted close to the base axis on a'relatively short crank arm and imparting at the position described, eliminates vibrational-torque, allowing a most eflective operation withaminimum amount of power,

, being driven at relatively high speed to afford heavy and eifective striking blows in rapid succession. Th1S' makes a partlcularly desirable hammer for use with electrical power "where the available voltage is limited and where a small motor must be used in order to I keep down theweight of the tool.

The foregoing description andaccompariy 7 ing drawings clearly disclose a preferred ems bodiment of my invention, but it will be understood; that, this disclosure is merely illustrative and that such changes in the:in-' vention may bermade as are fairlywithin the scope and spiritof the following claims.-

WVhat I claimis r e 1. A power hammer-having a rotatable hammer: blockbifurcated deeper than its axis of rotation to provide a rear wall and an integral counter-balancing portion rearwardly of said wall, and a hammer member pivotally supported vbetween said bifurcations in offset disposition of the block axis to accommodate a: retractive movement of a portion of sa1d hammer member past the axis of sa1d v both'the retractive and extended movements block, said hammer member being conformed, cooperatively with the rear wall of said block, so as to normally position the plane of the I striking" face in approximate right angular disposition to a plane taken through the block and the hammer axes. i

wherein said rear wall affords a cushion'to of thehammer'member; V I

A power hammer having a rotatable hammer block bifurcated deeper than its axis of rotationxto present an uninterrupted channel projecting through and beyond the axis of rotation of said block, and a hammer member pivotally supported between said bifurcations, said pivot being eccentrically of the block axis so as to normally position the plane of the hammer striking face in approximate right angular disposition to a plane taken through theblock and the hammer axes, and affording retractive movement of a portion of said hammer member past the axis of said block, and said block having an integral rearwardly extending portion beyond the rear wall of said channel for coun'ter-balancingithe pivotal activity'of the hammer member, and meansrinterposed between said rear Wall andthe hammer member for cushioning, sa1d hammer member 1n both the retractive and'ext'ended-cycles of operation. 7

4. In a power hammer, a rotatable block,

to normally position the planeof the striking surface of said hammer member in approximate right angular disposition to a plane passing through said block and hammer axes, and means torotatively drive said block.

"In witness whereof, I hereunto subscribe my name this 25thday of February, D.

19 a y 7 I JAMES E. BRYAN.-

x 2; A p'ower hammer as defined in-claim 1, J 

